Method of and apparatus for hardening gears



Dec. 14, 1937. L SLADE 2,102,040

METHOD OF AND APPARATUS FOR HARDENING GEARS Filed Aug 4, 1934 Sheets-Sheet l IIIIIIIIIII L. D. SLADE .Dec. 14, 1937.

METHOD OF AND APPARATUS FOR HARDENING GEARS Filed Aug. 4, 1934 3 Sheets-Sheet 2 3nventor 03330 055026249 f mtomeg Dec. 14, 1937. 1.. D. SLADE 7 METHOD OF AND APPARATUS FOR HARDENING GEARS Filed Aug. 4, 1954 3 SheetsSheet 3 Zmventor Q 0% menu Patented Dec. 14, 1937 METHOD OF AND APPARATUS FOKHARD- ENING GEARS Leon D. Slade, Rochester, N. Y., assignor to Gleason Works, Rochester, N. Y., a corporation of New York Application August 4, 1934, Serial No. 738,570

25 Claims.

The present invention relates to the surface hardening of metal articles and particularly to the surface hardening of gears and more especially of tapered gears such as bevel and 'hypoid gears. In a still more particular sense. this invention relates to a method and apparatus for surface-hardening gears in which a blow-torch by the blow-torchand then allowing the air to cool and harden them.

In the surface-hardening of gears, it has been the practice heretofore simply to traverse a flame go along the tooth surface to be treated and progressively quench the tooth immediately after it has been treated. Generally speaking, the surface-hardening apparatus heretofore built falls into two different classes. In one type of apparatus, the heating flame is applied while the blow-torchis moving in one directionalong a side of a tooth only and the flame is shut oil at the end of the stroke and the gear is indexed while the blow-torch is being returned to original position preparatory to the hardening of another tooth. In the other type of apparatus the heating-flame is applied both on the forward and return strokes of the blow-torch, but the gear is indexed between strokes in opposite directions, one tooth being treated on a forward stroke and the next adjacent tooth being treated on the return stroke. In both forms of apparatus, a single torchonly has been provided and only one side of a tooth 4 has been hardened at a time. The second form of apparatus theoretically is more efllcient than the first, but has not been used to any appreciable extent because in such apparatus as has heretofore'been built the angular position of the blowtorch must be reversed between strokes .in oppo- -site directions and this involves complications. In the first form of apparatus, the return stroke is an idle stroke,'and, therefore, wasteful of time.

In both forms of apparatus, the heating-flame is required to raise the temperature of a cold tooth up to the intense heat required for hardening and therefore the rate of traverse of the torch along the tooth is comparatively slow. a The primary purposes of the present invention are to provide a method and apparatus for surface-hardening gears which will be more ellicient, faster, and more economical than surfacehardening methods and apparatus heretofore employed. To these ends, the heating-flame is first traversed in one direction along a tooth to pre heat the tooth and then is immediately traversed back along the same tooth to harden it. Then the gear is indexed. The preheating stroke of the blow-torch raises the temperature of the tooth to a point close to the hardening temperature so that on the subsequent hardening-traverse of the torch over this tooth, the torch is required to raise the temperature of the tooth a very much less amount than if the tooth were cold and hence the torch can be moved more rapidly during the hardening traverse than-has heretofore been possible and the hardening operation can therefore be accomplished in much less time and with much less cost than has heretofore been possible. Moreover, a preheated tooth will be hardened deeper than a tooth that is not preheated and this without applying excessive heat at the surface of the tooth. Further than this, by preheating there are less surface strains set up in the hardening process. This last feature is especially important if for any reason a tooth has to be hardened a second time. Without a pre heating stroke cracks are very liable to develop. The preheating stroke is always made at a fast enough speed so that the surface of the tooth 7 does not get to the hardening heat; otherwise it might crack on the hardening pass.

Still further, it is an object of the invention t provide apparatus for hardening both sides of a tooth simultaneously. This again is an improvement in efliciency and makes possible a further reduction in hardening time.

Another object of this invention is to provide apparatus having a simple adjustment for control of the speed of traverse of the torch on the hardening stroke so as to permit the speed of traverse of the torch to be varied to conform to the tooth thickness, tooth height, etc. of the gear to be hardened. This speed-control has a spe cial application in the hardening of tapered gears, where the speed of traversepan be varied during the traverse in order to take care of the change inthickness and height of the tooth from end to end. i

Another object of the invention is to provide simple means for controlling thepath of traverse of the torch, which is interchangeable so as to permit the same apparatus to be used to harden gears of different lengthwise tooth-shapes. A further object of theinvention is to provide area of the flame to suit the height of tooth of the gear to be treated..

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

A preferred embodiment of the invention is illustrated in the accompanying drawings in which:

Fig. 1 is a side elevation, with parts shown in section, of the surface-hardening apparatus as adjusted for hardening a bevel gear;

Fig. 2 is an enlarged plan view, showing the torches and spray. pipes and the traversing and control mechanisms therefor;

Fig. 3 is an enlarged side elevation of the parts shown in Fig.2;

Fig. '4' is an end view of the parts shown in Figs.

2 and 3, looking at the end opposite to that on the work-head employed when hardening pinions;

which the torches are mounted;

Fig. 5 is a diagrammatic view illustrating the construction and principle of operation of the hydraulic control mechanism; Fig. 6 is a sectional view through a preferred form of torch employed in practicing the present invention;

Fig. '7 is a bottom plan view of this torch; Fig. 8 is a fragmentary sectional view, showing and v Figs. 9 and 10 are diagrammatic views illustrating, respectively, the positions of the torches and spray -jets at the beginning of a hardening stroke and at thebeginning of the return preheat stroke.

The present invention has been illustrated in connection with apparatus set up for hardening the teeth of astraight bevel gear. Two blowtorches for burning oxy-acetylene gas are provided, and are so arranged that they heat opposite sides of a tooth of the gear simultaneously. There is a spray-jet provided in conjunction with each torch and arranged with relation to the torch so -that the tooth is sprayed progressively.

with a cooling medium, such'as water, immediately after it is heated up by the torch. The apparatus is provided with control bars or cams, which can be adjusted to cause the paths of the two torches to converge as they move from the large to the small end of a bevel gear tooth so that the torches will remain at a uniform distance from the sides of the tooth despite the lengthwise taper of the tooth itself. The two torches and their cooperating spray-jets are mounted'upon a;- movable ram, which is hydraulically operated to reciprocate the torches over the tooth and control valves are provided to control the speed of movement of the torches on the hardening stroke to compensate for the change in tooth thickness and height of the tooth from" end to end. A control valve is also provided to govern the speed of the .return or preheating stroke in accordance with and 10. It has straight teeth 20, 'whose' simple and inexpensive, semi-automatic, fluidpressure operated apparatus which with but slight or formed integral with a base-plate 30 which forms a support for the ram that carries the torches. This base-plate 3B rests upon the floor.

The distance of the work above the floor can be varied, as is required for gears of different sizes and for different types of gears, by use of a set of nesting interchangeable rings, of which three are shown in Fig. 1 and designated 3|, 32 and 33, respectively. These rings are provided with bores that align with one another and with the bore of the tripod 25. The spindle 21 is, therefore, journaled in the rings and the tripod.

One or all of the rings 3|, 32 and 33 can be removed to vary the height of the work above the floor or additional rings can be added if required. A: ball bearing 35 is provided to be interposed between the shoulder of the work-spindle and the upper face of the uppermost ring or the upper face of the tripod in case all of the rings are re-' moved. This ball-bearing allows of free turning movement of the work-spindle.

The gear G is mounted on the centering-plate or arbor 38. This seats against the upper face of the work-spindle and is provided with a tapered projection 31 that fits into a correspondingly tapered portion of the bore' of the workspindle. The arbor is secured to the workspindle by the draw-bar 38. The head of this draw-bar engages a plate 39 which is adapted to seat against the lower face of the bearing portion of the tripod.

There are a pair of torches provided with the apparatus illustrated. These are designated A0 and 4!, respectively. Preferably water-cooled torches are employed, as shown.

The torches are secured to oxy-acetylene feedpipes 42 and 43, respectively. These pipes are secured in blocks 44 and 45, respectively (Figs. 2, 3 and 5) and are connected by flexible tubing 46 and 41, respectively, with a pipe 48. The gasother, they are preferably sprayed with jets of water. To this end, a pair of spray-pipes 54 and 55 are provided. These operate, respectively, in conjunction with the blow-torches 40 and 4!. The spray-pipes are preferably made of a flexible copper tubing so that they can be readily bent to direct the liquid used as the quenching medium on the tooth surfaces at points immediately behind the torches. I

The pipes 54 and 55 are also secured in the blocks 44 and 45, respectively. They are connected by flexible hose 56 and 51, respectively, with a single Y-pipe 59 and this is, in turn, connected through a hand-operated valve 60 with a casing 62 to which is connected the water-supply pipe 63 through which water is pumped to the casing from any suitable source.

In the apparatus shown, water is employed for cooling the torches. It is supplied tothe two torches from the casing 62 through a valve 65, the T 56, and the flexible tubing 68 and 69, respectively.

The blocks 44 and 45 are slidable transversely supporting bracket 16 and is held in these ways by gibs 11 and 18 which are secured to this bracket by screws 19.

The bracket 16 is trunnioned on the head 80 of a' cylinder 82 to which further reference will be made later, the pin 8I serving as a journal on which the bracket 16 is angularly adjustable.

The bracket 16 carries a cylinder 84 in which the piston 85 isreciprocal. There is a piston-rod 86 secured to this piston 85. This piston-rod projects through the front end wall 81 of the cylinder 84 and is connected by the pin 88 with the bracket 15 and its integral head 10. The pin 88 serves also to connect a plate 89 with the bracket and head. I

The plate 89 reciprocates with the head 15. It slides in ways 93 provided on the top wall of the cylinder 84. The plate 89 carries a trip-lug 90, the purpose of which will be described hereinafter. This trip-lug is longitudinally adjustable along a longitudinal slot 92 formed in the plate 89 and is held in any adjusted position by means of the bolt 9| which engages in this slot.

The plate 89 also carries an angularly adjustable cam-bar or plate 94. This is pivotally mounted on a bolt 95 that threads into the plate 89 and is held in any position of its angular adjustment by the butterfly nut 96 which threads upon a' bolt that is secured in the plate 89.and passes through an arcuate'slot 91 in the cam-bar that is concentric with the pivot-bolt 95. The cam-bar 94 is graduated at one end to read against a zero mark on a lug 98 that is secured by the screw 99 to the upper face of the plate 89.

At one side of the cylinder 84 there is mounted a housing I for a reverse valve IOI. At the other side of the cylinder there is mounted a housing I02 which contains a pair of throttlevalves I03 and I04, which are shown in section in Fig. 5. The reverse-valve controls the directions of movement of the head under actuation of the piston 85. The throttle valves control the speed of this movement in one direction, namely, during the hardening stroke.

There is a rod I06 secured to the stem of the valve I03 by a pin I01. This rod slides in a guide-bore provided on the valve-casing I02 and at its free end, the rod I06 carries a, roller I08 which is adapted to engage and ride on the side surface of the cam-bar 94. The roller I08 is held against the bar 94 by a coil-spring I09 which is interposed between the valve-stem I03 and the plate I I0 that closes the bore of the casing I02 in which the valvel03 slides. The spring I09 sur rounds a pull-rod II 2 which is secured to the valve-stem I03 and which extends through an opening in the plate H0 and has a knob H2 at its outside end to permit manipulation of the valve I03.

The valve-casing I02 is provided with an inlet port H5 and an outlet port H6. The valve I08 is provided with cylindrical guide surfaces or lands H1 and H8, respectively, adjacent its two ends. The valve has'a beveled portion II9 merging with the cylindrical portion H8 and controlling the area pf the port-opening H5. The cylindrical land I I1 is connected with the beveled portion I I9 by a portion I20 of reduced diameter. The area of opening of the port II5 controls the rate of movement of the piston 85 and is controlled in turn by the setting and shape of the cam-bar 94, as will hereinafter be described more particularly.

The valve I04 provides a basic control over the speed of movement of the piston 85 during the hardening stroke which is independent of the position of the valve I03. The valve I04 is of the same general construction as the valve I03 having cylindrical guide portions I25 and.l26 at its opposite ends with a beveled portion I21 merging into the cylindrical portion I26 and with the beveled portion I21 connected to the guide portion I25 by a cylindrical portion I28 of reduced diameter. The beveled portion I21 controls the area of opening of the inlet port I29, The exhaust port is indicated at I30.

The valve I04 is pressed toward full-open position by a coil-spring I32 which is interposed between the inner end of the valve and the end- .plate I33 of the valve-casing I02. The area of opening of the port I29 can be adjusted by rotation of a knurled-nut I34, which threads onto a collar I35 that is formed integral with the plate I36 that closes the outside end of the bore in which the valve I04 reciprocates. The nut I34 is pinned to a rod I31 which passes through the end-plate I36. Its inner end is of reduced diameter and engages a ball I38 that is seated in a recess I39 formed in the valve-stem I04. The sleeve of the knurled-nut I34 is beveled at its inner end and the beveled portion is graduated to read against a zero mark on the sleeve I35 to permit accurate adjustment of the valveopening.

The reverse valve IOI is of usual construction. It is moved in one direction by a coil spring I 40 which surrounds the valve-stem MI and is interposed between one end of the valve and the plate I42 which closes the adjoining end of the valve-casing I00. The valve is moved in the opposite direction by hand-lever I44. This lever is pivoted at I45 on a lug I46 formed integral with a side wall of the cylinder 80. This lever I44 is connected to the valve-stem MI by a link I41.

The reverse valve is adapted to be releasably locked .in the position to which it is moved maniially. To this end, the lever I44 is formed with a lug I50. This is adapted to be engaged by the lock-dog I5I. The lock-dog I5I is pivotaily mounted on a lug I52 extending from the casing I00 of the reverse-valve. The lock-dog is constantly pressed toward locking position by a spring-pressed plunger I 53 which is housed in the lug I52.

To produce a return or preheating movement of the piston 85, the lever I44 is swung from the position shown in Fig. 5 to the position shown in Fig. 2. The lock-dog I5I engages and holds the lever in this latter position until at the end of t the return movement of the piston 82, the tripdog 90 engages the tail of the lock-dog, disengaging the lock-dog from the lug I50 and releasing the lever. Then the spring I40 acts to reverse the valve IM and effect automatically 9. forward movement of the piston.

The blocks 44 and 45 previously described are pressed apart by a coil-spring I68 which is interposed between their opposed inner faces. This spring is mounted on a rod I 6| whose opposite ends enter holes in the opposed faces of the two blocks. At its outer end, each of the blocks 44 and 45 carries a roller I62.

These rollers I62 are arranged to ride on cambars I63 and I64, respectively, which are plvotally mounted for adjustment upon the upperface of the bracket 16. The cam-bars I83 and I64.

adjust about studs I65 and I66, respectively, that thread into the bracket'16. The bars are secured in adjusted positions by bolts I61 and another depending upon the shape and setting of the cam-bars I83 and I04. Thus as the torches and jets move longitudinally along a tooth, they may also lee moved transversely to maintain them at a uniform or at varying distances from the sides of the tooth.

The bracket 16, as above m entioned, is tru'n- I nioned on the head 80 of a, cylinder 82. To adjust the bracket 18 angularly about its pivot point a worm shaft I is provided. This worm shaft is suitably journaled externally on the cylinder 82 and the worm which it carries, meshes with a worm-wheel segment I16 which is secured to or integral with the bracket 16.

The cylinder 82 is vertically movable upon a relatively stationary piston I18. The movement of the cylinder 82 upon the piston I 18, which is for adjustment of the height of the blow-torches, is controlled by a hand-operated three-way valve I80. This valve controls the connection of a supply-line I8I or an exhaust-line I82 with the pipe I83. The supply and exhaust lines-are suitably connected to a pump and sump (not shown), respectively. This pipe I83 is connected to a duct I 85 that is drilled in the foot or base I80 of the piston I18, and this duct I85 is connected with a vertical duct I86 that leads through the piston I18 and has a port-openirrg I81 to the space in the cylinder above the top of the piston. It will readily be seen that when the valve, I80 is turned so as to connect the supply-line I8I with the pipe I83, the cylinder 82 will move vertically upwards on the piston I'IB and that when the valve is t-urnedso as to connect the exhaust line I82 with the pipe I83, oil above the piston I18 will be exhausted from the cylinder and the cylinder can be lowered on the piston.

The cylinder 82 is rotatable on the piston I18 to align the torches with a tooth'of the gear to be hardened. To hold the cylinder in the vertical position to which it has been adjusted while it is being rotated for angular position, a. split clamping-collar I80 is provided. By releasing the clamping-bolt I89, this collar can he slid alone the piston until it engages under the cylinder and then by tightening up the clamping bolt I89 again, the collar can be clamped to the piston to securethe cylinder against downward movement on the piston.

The cylinder itself is formed to provide a splitcfamp at its lower end andafter it has been adinto the base-plate 30 to which reference has already been made. Horizontal adjustment of the piston base I90 on the base-plate is efiected by rotation of the stub-shaft I92 which is rotatably mounted in the base I90 of the piston and which carries a spufipinion I93 that meshes with the teeth of a rack I94 which is secured to the base-plate 30. The horizontal adjustment described permits of moving the torches toward or from the work-spindle to accommodate gears of different diameters. I shall now describe the operation of hardening a straight bevel gear suchas the gear G shown.

The gear is positioned on the arbor 36 and the gear and blow-torches are brought intomperative relation by horizontal adjustment of the piston-base I90 on the base-plate30, by vertical adjustment of the cylinder 82 on the piston I18, by angular adjustment of the cylinder 82 on the piston I18, by angular adjustment of the bracket I16 on the cylinder 82 and by vertical adjustment of the work-spindle 21 on the tripod 25 through use of the interchangeable, nesting rings which are provided with the apparatus. The interchangeable rings allow of a rough adjustment of the vertical positions of the torches and gear relative to one another, whilea finer'vertical adjustment of the relative positions of the torches and gear is permitted by movement of the cylinder 82 on the stationary piston I18. For a straight bevel gear, cam-bars I63 an I64 having straight guide-surfaces, such as shown, are used. These bars are adjusted angularly on the bracket 16 so that the guide-surfaces of the bars are inclined to one another at an angle equal to the angle of convergence of opposite sides of the teeth of the bevel gear to be hardened and so that the guide surfaces are parallel tothe opposite sides of a tooth of the gear. The graduations permit of setting these bars accurately.

The throttle-valve I04 is adjusted by the knurled nut I34 to determine the basic speed of movement of the blow torches on the hardening stroke. This adjustment is determined by experience and can be made very fine because of the .graduations 0n the sleeve of the nut. The cam-bar 84 is adjusted angularly on the plate 81 to determine the variation in speed of traverse of the blow-torches as they move along a tooth of the gear in the hardening stroke. There are a number of factors which enter into the set ting of the cam-bar. Among these are the pitch 'of' the gear, the change in thickness of the teeth of the gear from end to end and the change in height of the teeth from end to end.

The trip-dog 90 is adjusted along the slot 92 to govern the length of stroke of the ram 10. This depends upon the length of face of the gear to be hardened.

The normal inoperative position of the parts of the apparatus is shown in Fig. 5. To harden a tooth of the gear, the operator throws the hand-lever I44 from the position shown in Fig. 5 over to the position shown in Fig. 2. .The locking-dog It" automatically locks the lever I44 in this latter position, the dog being automatically engaged with the lug I50 of the hand-lever under actuation of the spring-plunger I53. The spring I40 is, of course, compressed in the movement of the hand-lever from right" to left.

With the handelever in the position of Fig. 2, the hydraulic motive fluid flows' from the supply line 200 (Fig. 5)., which isconnected in any suitable manner to a pump (not shown), through the duct 20l into the left-hand end of thecylinder 84 and exhausts from the right-hand'end of the cylinder 84 through the duct 202 and the exhaust line 203', the latter flowing back to the sump (not shown). This causes the piston 85 to move to the right carrying with it the blow-torches 40 and 4I and the spray-jets 54 and 55 and the torches will preheat the tooth surfaces. The spray-jets 54 and 55 are ahead of the torches in the rightward direction of travel, and the water has no appreciable effect.

There is a manually adjustable throttle valve 204 in the exhaust line 203. This may be a v globe valve of any usual or suitable construction.

hand-lever I44. The spring It permits of adjusting the rate of the preheating movement to conform to the size of the teeth of the gear to be hardened. It is adjusted in each case so that the preheating movement will be quite rapid and the surface of the tooth will not be heated to the hardening temperature.

As the piston moves to the right it will be noted that the two torches and the respective spray-jets associated with each are spread -further and further apart due to the setting of the cam-bars I 63 and I64 and the action of the spring I60 on the blocks 44 and 45 which carry the jets and torches.

Toward the end of the rightwardor preheating traverse of the piston, the trip-dog 90 engages the tail of the locking-dog I5I and swings this locking-dog about its pivot to release the I40 then immediately moves the valve I M and with it the handlever over to the right to the position shown in Fig. 5. This reverses the valve IOI. The motive fluid now flows from the supply-line 200 through the duct 202 into the right-hand end of thecylinder 84 and the'left-hand end of the cylinder is on exhaust. This causes the piston 85 to move back to the. left.

The exhaust is through the duct 20I and the line 205. This line divides and has twobranches, designated 205a and 205b, respectively. The exhaust-fluid flowing through the line 205a passes through the throttle-valve I04 and flows back to the sump through the line 206. The rate of exhaust from the line 205a is determined by the setting of the nut I34, as described. The fluid exhausts from the line 2051) through the throttlevalve 203 and the line' 201 which-flows back to the sump. The rate of exhaust from the line 2051) is determined by the setting of the cambar 94.

The movement of the piston 85 to the left is comparatively slow because the motive fluid from the left-hand end of the cylinder must ex- I haust through the valves I04 and I03. It will be noted that with the setting of the cam-bar shown in Fig. 5, the speed of travel of the blowtorches will accelerate as the piston 85 moves from the right to the left. The section of the gear teeth grows thinner'from the large to the" small end of the teeth and the accelerated travel 'of the blow-torches in this direction allows of properly heating the teeth at all points along their length and at. the same time prevents burning of the teeth at their thin sections.

As the piston 85 moves from the right'to the left, the blow-torches are also brought closer and closer together. This is becausethe cam-bars I52 and I54 acting through the rollers I62 force the blocks 44 and 45 together against the resistance of the spring I80. .The blow-torches are, therefore, maintained at a uniform distance from the sides of a tooth as they-move" along the tooth.

' In this movement ,of the piston 85 from right to left, the blow-torchesprecede the spray-jets.

v The torches progressively heat up the side of a tooth to a high intensity. The spray-jets following immediately quench the heated portions of the tooth, and thus the sides of the tooth are progressively hardened.

The forwardbr hardening traverse of the torches stops when the piston 85 bottoms in the left-hand end of the cylinder. The operator then indexes the gear G tmbring the next tooth of the gear in line between the blow-torches and then he throws the lever I44 from the position shown in Fig. 5 over to the position shown in Fig. 2 again, so as to start the return travel of the piston 85. In this return travel of the, piston thetorches will preheat the new tooth of the gear, as already described. 1

Any suitable type of indexing mechanism may be provided, but in the apparatus shown the indexing is intended to be effected by handby simply rotating the gear manually. This requires no effort because the work-spindle is mounted on anti-friction bearings. The gear is held inits indexed position by a detent that is adapted to be engaged in the tooth spaces of the gear.

This detent is shown in Figs. 2 and 3. It comprises a hand-lever 2I0 that carries a ball-tipped pin 2I2. The lever is pivotally mounted at 2I3 on a block 2I4 which is pinned to a bar 2 I5. The bar 2I5 is slidably mounted in a bracket 2I6, which is secured by means of a T-bolt 2I'I to the underside of the bracket 15. The head of the T-bolt engages in a T-slot 2I8 (see Fig. 1)

- 220 holds the ball 2 I2 in engagementwith a tooth space of the gear, preventing rotation of the gear during the hardening operation.

It will be noted from Figs. 2 and 5 that at their left-hand ends, the cam-bars I68 and I84 are sharply beveled ofl, as denoted at 225 and 225 respectively, providing guide-surfaces that, diverge sharply from one another. The purpose of these outwardly beveled portions is to move the torches 40 and 4I quickly away from one another after they pass beyond the inner end of the gear tooth so as to prevent the intensity of the flame from one torch melting the opposite torch.

Figs. 9 and i0 illustrate diagrammatically two successive steps in the. hardening of a bevel gear. In Fig. 9, the torches 40 and 4I and the spray-jets 54 and are: shown in position as they move along the'sides of the tooth 20 of the gear G on a hardening stroke. As they move toward the small end of the tooth their paths converge as long as they are in operative relation with the tooth. When the torches pass beyond theend of the tooth, h owever,they are quickly spread apart through operation of the spring I80 causing the rollers I62 to follow the diverging portions 225 and" 226 of the guidesurfaces of the cam-bars I 83.,and I64. The operator then indexes the gear, bringing the tooth I 20b into operative position. Then he reverses the lever I46 to cause the torches to make the return preheating traverse along the sides of the tooth 2017.. In Fig. 10, the'torches and jets are shown still spread apart just prior to the return preheating movement. At the end of the return movement, the piston is automatically reversed, as described, and the torches again traverse the tooth 2% but in the opposite direction and the tooth is hardened.

The first operation on a tooth is the preheating traverse and then follows the hardening traverse. At the end of the hardening traverse, the

gear is indexed.

For difierent types of gears, difierent worksupports may be provided. Fig. 8 shows a worksupport for a bevel pinion. In this case a spindle 230 is provided to take the place of the spindle 21. This spindle 230' is constructed so as to be substituted directly for the spindle 21 on the work-support and take its bearing on the anti-friction bearing 36. The spindle 23B is formed with a head 235which is bored at right angles to the axis of the spindle. The bore in the head 235 is adapted to receive a second spindle 232 which is mounted on anti-friction bearings 233 and 234 in the bore of the head.

The pinion P to be hardened is mounted upon an arbor 238 which is secured by the draw-bar 237! in a sleeve 238 that has a pressed fit in the spindle 232. The draw-bar is tightened by threading up on the nut 239. This nut through its cooperating washer engages a circular plate 2 30 which has a portion of reduced diameter that fits into a second circular plate 265 that engages the outer race of the anti-friction bearing 236. Therefore, by tightening up the nut 239, the arbor 237, sleeve 238, and spindle 232 are all held in place. An eye-bolt 262 is threaded into the head 235' so that the head can be lifted readily out of the tripod and ring when it is desired to change work spindles.

It will be noted that when a work spindle is used, such as has just been described, that the teeth of the pinion will have a reverse relation to the torches as compared with the teeth of a a in the reversed relation from that shown in Figs.

2 and 5 so that the torches may converge as they travel from left to right and diverge as they travel from right to left.

While the invention'has been described particularly in connection with the hardening of straight tooth bevel gears, it will be readily understood that the invention is applicable to the hardening of all types of gears and further that with but slight change, the apparatus illustrated can be used for'hardening various" types of gears. Thus, in order to harden straight tooth spur gears, a suitable work-spindle may be provided and the torches can-be caused to travel in parallel paths, as required to harden opposite sides of the teeth of such gears, by simply setting the cam-bars I63 and I 64 to zero positions so that their guide-surfaces are parallel. I

For the hardening -of helical spur gears the cam-bars E63 and I64 will be adjusted so that theirguide-surfaces are parallel but are inclined angularly in accordance with the helix angle of the teeth of the gear to be hardened.

For longitudinally curved tooth gears, such as spiralbevel and hypoid gears, cam-bars having curved guide-surfaces will be used instead of. the

cam-bars I53 and IE4. The guide-surfaces of the bars will beof a curvature to correspond to the lengthwise curvature of the teeth of the gear to be hardened and the bars will be adjusted Any suitable type of blow-torch'may be used for the hardening of gears according to the present invention. A preferred form of blow-. torch is illustrated, however, in Figs. 6 and 7.

The oxyacetylene gas mixture enters the torch through the bore 25% and flows through the ducts 25! and 252 into the duct 253 which is parallel to the duct 25B. The flame-openings 254 connect with the duct 253 and extend diagonally from one side of this duct, as clearly shown in Fig. '7. This is a very important feature as can be seen from Fig. 10, for when the torches have moved clear of the tooth at the small end there of, the flames from the two torches are not directed against one another but diagonally and forwardly. With this torch-construction and with the separation of the torches at the small end of the tooth, the possibility of the flame from one torch melting the other torch is obviated. Each torchis so arranged that the fiame-open ings extend up the sides of the tooth. When a gear of considerable tooth height is to be hardened, allof the flame-openings will be in use, but provision is made for the closing off of one or more of these openings when gears of smaller tooth height are to be hardened. The means for closing ed the upper flame-openings comprises a valve-rod 255 which is threaded at its upper end into the duct 25-3 and which is manipulated by the knob or handle 258. The torch is cooled by water which enters the duct 258 through the opening 25S to which one of the tubes 68 or 69 is connected. The water exhausts through the openings 2%.

The invention has been described in connec-' tion with an apparatus which is semi-automatic in operation. It is within the contemplation of the invention, however, to provide-fully automatic apparatus if desired.

In general'it may be said that while the invention has been described in connection with certain particular embodiments, it is capable of still further modification and this application is intended to cover any variations, uses, or adaptations of the invention, following, in general, the

principles of the invention and including such departures from the present disclosure as come Within known or customary practice in the art direction to bring the surface up to the temperature required for hardening.

2. The method of surface-hardening a gear which comprises traversing a flame along a tooth in one direction from end to end to pre- 3. The method of surface-hardening gears which comprises traversing a flame along a tooth in one direction from end to end at a relatively fast speed to pie-heat the tooth, immediately traversing the flame along the tooth from end to end in the opposite direction at a relatively slow speed to raise the tooth to the temperature required for hardening, and then indexing the gear.

4. The method of surface-hardening gears which comprises traversing a flame along a tooth in one direction from end to end to pre-heat the tooth, immediately traversing the flame along the tooth from end to end in the opposite direction to raise the tooth to the temperature required for hardening, quenching the tooth progressively immediately after it is raised to the hardening temperature, and then indexing the gear.

5. In apparatus for hardening gears, a pair of torches arranged, respectively, to direct intense flames simultaneously at opposite sides of a gear-tooth, means for traversing the torches along the sides of the tooth, and means for quickly moving the torches apart when they pass beyond one end of the tooth.

6. In apparatusfor hardening tapered gears, a pair of torches arranged, respectively, to direct intense flames simultaneously against opposite sides of a gear-tooth, means for traversing the torches along the tooth from end to end, and means for causing said torches to converge as they traverse the tooth from the large to the small ends thereof.

7. In an apparatus for surface hardening gears, a torch for directing an intense flame against a side of a gear tooth, a support on which the torch is mounted and means for moving the support in the direction of the tooth length to move the flame along the tooth surface, and means operable upon movement of the support for varying the velocity of movement of said support.

8. In apparatus for surface-hardening gears, a longitudinally reciprocable support, a pair of torches mounted on said support and movable thereon transversely of the direction of movement of said support, means for reciprocating said support to move the torches longitudinally of a gear tooth, and means adapted to control the transverse movement of the torches during the reciprocatory movement of the support.

9. In apparatusfor hardening gears, a movable support,a torch mounted upon said support and arranged thereon to direct an intense flame against one side of a gear-tooth, means for actuating said support to traverse the torch along the tooth from one end thereof to the other successively first in one direction and thenin the other, and means controlling the rate of movement of said support so that it is moved at a relatively high speed in one direction to cause the torch to preheat the tooth and at a relatively slow speed in the opposite direction to cause the torch to raise'successive portions of the tooth to hardening temperature.

10. In apparatus for hardening gears, a torch arranged to direct an intense flame against one side of a gear-tooth, means for traversing the torch along the tooth in one direction at a relatively high speed, means for automatically reversing the direction of movement of the torch at the end of said movement, means for moving the torch in the opposite direction along the tooth at a relatively slow speed, and means operable during movement of the torch in the latter direction to progressively quench the tooth im mediately after it is heated.

11. In apparatus for hardening gears, a reciprccable support, a blow-torch carried by the support and adapted to direct an intense flame against one side of a gear-tooth, means for reciprocating the support, and means operable by the support in its movement in one direction for varying the speed of its movement.

12. In apparatus for hardening gears, a rec procable support, a blow-torch carried by the support and adapted to direct an intense flame against one side of a gear-tooth, fluid-pressure operated means for reciprocating said support. and an adjustable throttle valve operable by the support in its movement in one direction for controllingthe speed of movement of the support in one direction.

13.1n apparatus for hardening gears, a reciprocable support. a pair of blow-torches carried by the support and adapted to direct intense flames against opposite sides of a gear-tooth simultaneously, means for reciprocating the support, and means operable by the support in its movement for vary ng the distance between said torches as they move along the tooth.

14. In apparatus for hardening tapered gears, a pa r of torches arran ed, respectively. to direct intense flames simultaneously against opposite sides of a gear-tooth, means for traversing the torches along the tooth from end to end thereof, means for causing said torches to converge as they approach the small end of the tooth, and means for accelerating the rate of movement of the torches as they approach the small end of the tooth.

15. In apparatus for hardening gears, a torch. a work support, a reciprocable slide upon which one of the aforesaid parts is mounted, means for moving the slide to move the torch relatively along the length of the gear tooth. and a cam for guiding said torch as it moves lengthwise of the tooth' to maintain the torch at a uniform distance from the s de of the tooth being treated.

16; In apparatus for hardening gears, a torch, a work support. a reciprocab e slide. a block upon which one of the first two parts is mounted, said block being mounted on saidpart and being reciprocable thereon in a direction transverse to the direction of movement of the slide, a relatively fixed cam having an operating surface parallel to the side surface of a tooth of the gear, and means operatively connecting said block to said cam.

17. In apparatus for hardening gears, a work support, a pair of torches, means for producing relative longitudinal movement between the torches and the work support to move the torches from one end of a gear tooth to the other, and means for producing relative movement between the torches and the work support in a direction transverse to said longitudinal movement to cause said torches to remain at uniform distances, respectively, from opposite sides of a tooth of the gear as they move from one end of the tooth to the other.

18. In apparatus for hardening gears, a work support, a pair of torches, a slide, a pair of blocks, in which the torches are mounted, movable transversely on the slide, and means for moving the blocks transversely as the slide moves longitudinally of a gear tooth to maintain the torches at uniform distances, respectively, from the sides of the gear tooth. I

19. In apparatus for hardening gears, a work support, a pair of torches, a slide, a pair of blocks, in which the torches are mounted, transversely movable on the slide, and means operable on movement of the slide for moving tr blocks transversely of the slide.

20. In apparatus for hardening gears, a work support, a pair of torches, a slide, a pair of blocks mounted on the-slide for movement transversely thereof, a pair of fixed cams extending longitudinally of the slide-and having operating surfaces, respectively, in parallelism with opposite sides of a tooth of the gear, and means operatively connecting said blocks, respectively, to said cams to move the blocks transversely on the slide on movement of the slide.

21. In apparatus for hardening tapered gears,

a work support, a pair of torches, aslide, a pair of blocks mounted on the slide for movement transversely thereof, a pair of cams having straight guide surfaces adjustable into converging relation to be parallel. to opposite sides of a tooth of the gear, and means operatively connecting said blocks, respectively, to said cam-guides.

22. In apparatus for hardening gears, a work support, a torch, aslide on which one of said parts is mounted, fluid-pressure operated means for reciprocating said slide, a frame on which the slide is reelprocable, a cam and a throttle valve, one of which is mounted on the slide and the other on the frame, said cam having an operating torch, means for controlling the movement of I said slide so that it moves at a faster rate on the preheating stroke than on the hardening stroke, a reverse valve controlling the direction of movement of the slide, and means carried by the slide for automatically tripping the reverse valve at the end of each preheating stroke.

24, In apparatus for hardening gears, a work support, a pair of torches for'heating opposite sides of a tooth of the gear simultaneously, a

for reciprocating the slide to efiect preheating and hardening movements of the torches, and means for moving the torches apart at the end of each hardening stroke.

25. In apparatus for hardening gears, a work support, a reciprocable slide, a pair of blocks mounted on the slide for movements transversely of the direction of movement of the slide, a pair of torches mounted in the blocks and arranged to operate simultaneously on opposite sides of a tooth of the gear, said torches having flame openings directed diagonally at the sides of the gear tooth and toward one end of the tooth, relatively fixed cams extending in the direction of movement of the slide, and means operatively connecting the blocks with said cams, said cams 1 being so formed as to cause separation of the torches when they pass beyond the described end of the tooth.

LEON D. SLADE.

slide on which the torches are mounted, means 1 

